Polyamines are ubiquitous components of living organisms. They are implicated in cell division (including cancer growth), differentiation, and protection against adverse environmental conditions through stabilization of membranes and nucleic acids. Stress-tolerant genetic lines of crop plants accumulate uncommon long-chain polyamines, such as thermine and caldopentamine, in response to drought, high temperature and other abiotic stresses. Stress-susceptible genetic lines of these plants exhibit a net loss of polyamines upon stress. A primary objective of this research is to identify how polyamine biosynthesis is regulated at the enzymatic and genetic levels in drought-tolerant alfalfa and heat-tolerant cotton. Three key enzymatic activities are responsible for the biosynthesis of all polyamines from putrescine in alfalfa and cotton. Each of the three enzymes will be purified and used for preparation of antibody probes for study of the respective eyzymatic distribution and regulation, and for preparation of cDNA probes. The cDNA probes will be used for study of the genetic regulation of polyamine biosynthesis and for isolation of the corresponding full-length genes. Genetic coding sequences will be transformed into stress-susceptible lines for study of their transgenic expression and regulation, and to test the hypothesis that some combination of these genes are necessary for expression of stress-tolerance. The isogeneic sets of materials thus derived will be useful in studies of the mechanistic roles of the polyamines. Also, cotton cell line variants (possible genetic mutants) exhibiting resistance to specific inhibitors of the three enzymes have been generated that overproduce polyamines through alterations in enzymatic activity. These materials will be used to study certain aspects of the enzymatic regulation of polyamine biosynthesis. The basic information generated from these studies will have value in the elucidation of the fundamental cellular and molecular roles of the polyamines in living organisms. Thus, these results may have future practical application in developing superior medical therapies against adverse environmental conditions, or perhaps to treat cancer.